Formation and annihilation of stressed deformation twins in magnesium

Karim Louca (1) , Hamidreza Abdolvand (1) , Charles Mareau (2) , Marta Majkut (3) , Jonathan Wright (3)

1 UWO - University of Western Ontario
2 LAMPA - Laboratoire Angevin de Mécanique, Procédés et InnovAtion
3 ESRF - European Synchrotron Radiation Facility [Grenoble]

The mechanical response of polycrystalline materials to an externally applied load and their in-service performance depend on the local load partitioning among the constituent crystals. In hexagonal close-packed polycrystals such load partitioning is significantly affected by deformation twinning. Here we report in-situ compression-tension experiments conducted on magnesium specimens to measure the evolution of grain resolved tensorial stresses and formation and annihilation of twins. More than 13000 grains and 1300 twin-parent pairs are studied individually using three-dimensional synchrotron X-ray diffraction. It is shown that at the early stages of plasticity, the axial stress in twins is higher than that of parents, yet twins relax with further loading. While a sign reversal is observed for the resolved shear stress (RSS) acting on the twin habit plane in the parent, the sign of RSS within the majority of twins stays unchanged until twin annihilation during the load reversal. The variations of measured average stresses across parents and twins are also investigated. Load partitioning to grains during deformation of a polycrystalline material is affected by the presence of twins. Here, synchrotron diffraction is used to study 1300 twin-parent grains, revealing that stress is higher in twins than in the parent grain during the early stages of plastic deformation.

Mots clés: NUCLEATION; STRAIN; ALLOY; GRAIN; TITANIUM; FIELDS; GROWTH; STATE; SLIP; AZ31

Domaines: Physique [physics]

Karim Louca, Hamidreza Abdolvand, Charles Mareau, Marta Majkut, Jonathan Wright. Formation and annihilation of stressed deformation twins in magnesium. Communications Materials, 2021, 2 (1), pp.9-1-9-11. ⟨10.1038/s43246-020-00105-y⟩. ⟨hal-03722636⟩